The present invention relates to an electric apparatus which uses an electric part that is large in heat generation and that also becomes a source of generating electromagnetic noise and, in particular, to an electric apparatus which can be suitably used for an inverter, transformer or noise filter and can realize its size reduction, high heat radiating efficiency and high electromagnetic shielding properties.
There has been conventionally proposed an electric apparatus in which a casing (case) for accommodating therein an electric part providing a large quantity of heat generation is made of such heat conductive material as aluminum and the casing is provided on its outside with heat radiating fin parts.
FIG. 12 is an outside appearance of an electric apparatus provided with a conventional heat radiating fin. In the drawing, reference numeral 801 denotes a base, numeral 802 denotes a fin part, and 803 denotes a main body casing. Mounted on an outside of the casing is the base 801 on which a row of many planar fin parts 802 are provided for heat radiation through the base 801 and the entire fin part row.
For the purpose of increasing its heat radiation efficiency, the conventional electric apparatus is arranged to make a surface area (heat radiation surface) of the heat radiation fin as wide as possible. For this reason, when an electric part providing a relatively large quantity of heat generation is used, there has occurred such a problem that a volume ratio of the fin parts to the entire volume of the electric apparatus becomes large and thus the apparatus becomes large in size.
In such an electric apparatus as an inverter or converter device using semiconductor switching elements such as GTOs (gate turn-off thyristors) or IGBTs (insulated gate bipolar transistors), there are many cases where electromagnetic noise externally radiated by the turning on and off operation of the switching element has an adverse influence on the other electronic parts within the apparatus or on electronic devices other than the apparatus.
Further, as the number of electronic devices and the number of types used increase, electromagnetic noise generated by these devices has been increased. To avoid this, it is required for the electric apparatus to have such a high electromagnetic immunity that prevents the apparatus from being erroneously operated in response to external incoming noise.